This invention relates to a method and apparatus for interfolding and, more particularly to the interfolding of lightweight webs at high speed and in an efficiently used space. This invention is an improvement upon Shirasaka Application Ser. No. 666,224, filed Mar. 11, 1976, now U.S. Pat. No. 4,052,048.
In the above-identified application, a novel structure and method was provided utilizing identical folding plates for the longitudinal interfolding of one-half lapped webs, i.e., for V folding. Previously, V folding had been achieved longitudinally but with much longer machines because right and left hand folding plates were employed -- making the machines almost twice as long.
In contrast to the V folding which had been performed in longitudinal fashion previously, Z folding has been performed commercially in transverse fashion. Although rotary machines for transverse folding can operate at substantial speeds, they operate on but a single web and therefore are much less efficient than longitudinal folding where literally hundreds of webs are processed simultaneously. Z folding is particularly advantageous -- as for packaged toweling -- because a much longer length of towel can be dispensed (as from a wall dispenser) without increasing the depth of projection from the wall. For example in contrast with V interfolded towels, the Z folded (for the same depth of dispenser) yields a towel sheet 50% longer. Thus, many users of hand towels prefer the Z folded version.
In light of the demand for more efficient Z folding equipment, it was decided to attempt to Z fold using folding plates made according to the above identified Shirasaka application. The Z folding was achieved by the folding plates but some difficulty was encountered in thread-up, i.e., advancing a Z folded web from an "upstream" folding plate toward and underneath the next downstream folding plate. To ease the thread-up procedure, I remove the tongue which projects forwardly from the side of the folding device creating the overfold. This not only resulted in a satisfactory Z fold but one considerably easier to thread and further functions equally well for V folding.
Thus, I have provided an even simpler folding plate than that of the above identified application but which possesses undiminished the space and adjustability advantages thereof but even further facilitates threadup. With all of these advantages, it was surprising to me that they were not appreciated previously in a structure somewhat similar as set forth in U.S. Pat. No. 3,679,095. There, however, the folding plate was used for what might be termed a "partial" Z fold and this only for the top layer of a stack of V folded tissue webs.